In general, the so-called electroreduction water obtained in a cathode chamber by electrolyzing an electrolytic solution of sodium hydroxide or the like is regarded as having active oxygen eliminating activity and DNA strand break inhibiting activity in the body. This is regarded as resulting from reductiveness of active hydrogen contained in the electroreduction water.
The concentration of hydrogen radicals contained in the electroreduction water or the like influences the active oxygen eliminating activity in the body, and hence establishment of a detection method for hydrogen radicals as well as a quantitative analysis method therefor is required.
The term active hydrogen indicates a hydrogen radical readily causing chemical reaction by a method such as ultraviolet radiation or discharge, and hydrogen formed when acid acts on a metal or arising from a cathode side in electrolysis is also a hydrogen radical having high reactivity. The active hydrogen liberates a metal from alkali metal salt, and readily reduces oxides, sulfides etc. of various metallic elements to metals. Further, the active hydrogen forms a hydride with arsenic, phosphorus, oxygen, halogen, antimony, tin or the like, and forms formaldehydes with carbon monoxide and carbon dioxide. In addition, the active hydrogen causes addition, displacement or hydrogen atom abstraction reaction with various organic compounds, and adds hydrogen to an unsaturated organic compound. Hydrogen radicals, which are relatively stable as such, emit an extremely large quantity of heat and return to general molecules when coming into contact with a metal surface.2H.→H2+435 kJ/mol
The hydrogen radicals are detected through pressure difference when the concentration thereof is high, or through discoloration of tungsten oxide or the like when the quantity thereof is small. However, these methods for detecting hydrogen radicals formed in gas cannot be applied to measurement of hydrogen radicals present in water. Presence of hydrogen radicals in electroreduction water can be proved when the hydrogen radicals can be detected and determined by trapping the same with a water-soluble radical trap agent, and hence study has been progressed in order to establish a detection method and a determination method.
When only a water sample was employed or a water-soluble radical trapping agent of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and an aqueous solution sample were reacted with each other for measuring an ESR spectrum with an electron spin resonator (ESR), no spectrum of hydrogen radicals was recognized.
When hydroxide radicals were formed with a Fenton's reagent for confirming decrease of the hydroxide radicals by reducing power of an aqueous solution sample through an ESR spectrum, no clear difference was recognized. Thus, it has been considered difficult to detect hydrogen radicals present in electroreduction water by a method having low detection sensitivity due to low concentration of the hydrogen radicals.